Principal Investigator/Program Director (Last, First, Middle): Michel, Thomas PROJECT 3: "Regulation of Vascular Redox State byThioredoxin." Richard Lee,Project Leader Abstract: Thioredoxin is a powerful scavenger of reactive oxygen species. Thioredoxin-interacting protein (Txnip; also known as VDUP1 or Vitamin D3 Up-regulated Protein 1) binds to thioredoxin and is now known to be an important inhibitor of thioredoxin activity. We have previously shown that Txnip is itself a redox-sensitive gene with a protein product that impairs cell survival. Furthermore, Txnip overexpression blocks cellular growth responses, and growth factor signals such as PDGF require degradation of Txnip in order to allow thioredoxin- mediated transcriptional activity. Thus, compelling evidence has now emerged that Txnip, an obscure orphan gene product only a few years ago, is a critical regulator of diverse signaling events due to its direct inhibition of thioredoxin activity. Because intracellular thioredoxin levels tend to be constant, Txnip may therefore be a key mechanism for controlling intracellular redox state. Reactive oxygen species participate in many stages of atherosclerosis. Here we present preliminary data on the potential importance of Thioredoxin/Txnip in vascular disease and describe its potential role in accelerating atherosclerosis. An intriguing new finding is that while many stimuli suppress Txnip and thus increase thioredoxin activity, glucose robustly induces Txnip and inhibits thioredoxin activity both in vitro and in vivo. We propose exploration of the central hypothesis that regulation of Txnip impairs vascular thioredoxin activity, leading to increased oxidative stress and promoting atherosclerosis. Because glucose induces Txnip, these experiments have particular relevance to diabetic vascular disease. We describe three hypothesis-driven Aims that will explore the role of Txnip in vascular pathophysiology in vitro and in vivo. The Aims are: Aim 1. To test the hypothesis that the induction of Txnip by glucose promotes a pro-apoptotic state in vascular cells through blockade of thioredoxin's antioxidant function. Aim 2. To test the hypothesis that Txnip regulates redox state in diabetic arteries in mice using tissue-specific targeted gene deletion approaches. Aim 3. To test the hypothesis that regulation of Txnip participates in the promotion of atherosclerosis.